1. Field of the Invention
This invention relates to the field of medical devices. In one embodiment, this invention relates to the field of filmless dental radiography.
2. Description of the Related Art
In clinical practice, medical devices are very often used in conjunction with an auxiliary component. A common example is a conventional oral thermometer, which when used to take a patient's temperature, is covered with a protective sheath. The thermometer performs the primary function of taking a temperature and the sheath performs the ancillary function of providing a hygienic barrier between the thermometer and the environment within the patient's oral cavity. The auxiliary component in that situation serves only to provide the hygienic barrier, and does not serve other purposes.
Auxiliary components are also used in the field of filmless dental radiography. By way of general background, dentists and oral surgeons typically use x radiation to obtain images of their patient's teeth, mouths and gums to aid in diagnosis and treatment. In traditional oral and dental radiography, a cartridge containing photographic film is placed in the patient's mouth, for example behind a patient's tooth, and an x-ray beam is projected through the tooth and onto the film. The film, after being exposed in this manner, is developed in a dark room or a closed processor using special chemicals to obtain a photographic image of the tooth.
In the last several decades, the field of filmless dental radiography has emerged. In filmless dental radiography, an x-ray beam is still projected through the patient's tooth, but no photographic film is used. Instead, an electronic sensor is placed in the patient's mouth behind the tooth to be examined. The electronic sensor may include a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS) array or any other filmless radiation sensor. The x-rays pass through the tooth and impinge on the electronic sensor, which converts the x-rays into an electrical signal. The electrical signal is transmitted to a computer, either directly or through a module containing intermediate processing circuitry. The computer then processes the signal to produce an image on an associated output device, such as a monitor or a printer.
Filmless dental radiography offers several advantages over traditional film-based radiography. Most importantly, the electronic sensor is much more sensitive to x-rays than is film, allowing the dosage of x-rays to the patient to be lowered by as much as 90%. Also, the image of the tooth is generated by the computer almost instantaneously, thus eliminating the entire development process, including the use of potentially harmful chemicals. In addition, because the images are generated electronically, they can be stored electronically in a computer database.
Because electronic sensors, unlike film, are re-usable from patient to patient, it is common to use a sterile, x-ray permeable sheath that surrounds the sensor. For example, U.S. Pat. No. 6,811,312 depicts a sheath 12 that surrounds a sensor 10 and cable 14. Such sheaths are typically disposable, and are changed between examinations, so that no sheath is used for more than one patient. In this manner, the sheath protects the re-usable sensor from contamination. Protective sheaths, however, have heretofore been used only for the purpose of providing a hygienic barrier, and there has been little or no efforts at utilizing them for any other purposes.
On the other hand, conventional digital dental radiography systems are not without their drawbacks. For example, the connection between the sensor and the processing module or computer is most conventionally made via a cable. Such a cable, however, can be uncomfortable for and annoying to the patient in whose mouth the intraoral sensor is placed. The cable is also bothersome to the dental practitioner when positioning the sensor in the patient's mouth.
In addition, the repeated acts of positioning and re-positioning the cable, which involve a good deal of bending, twisting and pulling of the cable, puts mechanical stresses on the cable. These stresses can eventually lead to cable failure, and indeed cable-related malfunctions are one of most prevalent reasons for product failures and returns in this field.
One class of solution to this problem is to eliminate the cable altogether, and provide an electronic sensor that communicates with a processing module or computer over a wireless link. Such a solution has been set forth, for example, in U.S. Pat. Nos. 7,193,219 and 6,924,486. Such wireless solutions, while excellent for their intended purposes, increase the complexity of the sensor, and impose limitations on the amount of power available to the sensor. Accordingly, such solutions may not always be the most desirable.
Another solution that has been proposed is to utilize a removable cable, which can be attached to and detached from the sensor body by the dental practitioner. Such a solution is described in U.S. Pat. No. 6,030,119. This solution, however, does not solve all of the aforementioned problems. In particular, while this approach may be effective to minimize the mechanical stresses that are put on the cable, and to that extent increases cable life and reduces cable failure rate, it does little to address positioning problems and nothing to address patient comfort problems, since large protrusions are required to receive the detachable cable (see for example projected portions 43 shown in FIGS. 5 and 6 of U.S. Pat. No. 6,030,119). These protrusions hamper positioning efforts as much or nearly as much as the cable itself, and contribute significantly to overall patient discomfort.
The short-comings of the apparatus of U.S. Pat. No. 6,030,119 highlight why a wholly-satisfactory solution to the cable problem has heretofore been so elusive, namely as a result of the requirements of the cable itself. On the one hand, the cable must survive multiple cycles of bending, twisting and pulling during its lifetime, and in that sense it is desirable to make the cable as sturdy as possible. On the other hand, the cable should be flexible, soft, comfortable and utilize a connection junction as small as possible so as to provide simple positioning for the dental practitioner and allow comfortable placement in the patient's oral cavity during an x-ray exam. These requirements, which in a certain sense are at odds with one another, have heretofore prevented a solution which addresses all of the problems presented by the cable, including the positioning problems, comfortable problems and failure problems, without detracting from the overall performance of the system.
Accordingly, the problems presented by the cable in a wired digital dental radiography system have not been adequately solved. At the same time, the auxiliary component with which the electronic sensor is conventionally used, namely the sheath, has heretofore only served to provide a hygienic barrier between the sensor and the patient's oral cavity, and its presence and availability has yet to be exploited for any other purpose.